linux-kernel - [PATCH v1 1/3] powerpc/code-patching: Improve verification of patchability

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Date:   Fri, 24 Sep 2021 14:38:02 +0200
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        Michael Neuling <mikey@...ling.org>
Subject: [PATCH v1 1/3] powerpc/code-patching: Improve verification of patchability

Today, patch_instruction() assumes that is called exclusively on valid
addresses, and only checks that it is not called on an init address
after init section has been freed.

Improve verification by calling kernel_text_address() instead.

kernel_text_address() already includes a verification of
initmem release.

Cc: Michael Neuling <mikey@...ling.org>
Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 arch/powerpc/lib/code-patching.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
index f9a3019e37b4..20ec6648aacc 100644
--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c
@@ -190,10 +190,9 @@ static int do_patch_instruction(u32 *addr, struct ppc_inst instr)
 int patch_instruction(u32 *addr, struct ppc_inst instr)
 {
 	/* Make sure we aren't patching a freed init section */
-	if (init_mem_is_free && init_section_contains(addr, 4)) {
-		pr_debug("Skipping init section patching addr: 0x%px\n", addr);
+	if (!kernel_text_address((unsigned long)addr))
 		return 0;
-	}
+
 	return do_patch_instruction(addr, instr);
 }
 NOKPROBE_SYMBOL(patch_instruction);
-- 
2.31.1